The invention relates to a duct system, particularly for use as an intake manifold for an internal combustion engine, with flap valves in the individual intake ducts to the cylinders. The invention further relates to a process for manufacturing the described intake manifold.
Such an arrangement of flap valves in the individual intake ducts of an intake manifold is disclosed, for instance, in DE 38 43 509. Each of the cylinders has two separate intake channels for the combustion air. The flap valves permit the closing of one of the intake channels to the cylinders, which makes it possible to reduce the effective intake cross section for the cylinders in the partial load range of the engine. The flap valves may be controlled by means of a push rod, which is moved via a flap valve actuator. The flap valves move against a mechanical stop. As a result, they can only be operated in the open or closed positions. The elasticity of the connecting rod is deliberately used to compensate for manufacturing tolerances through deformation in the stop positions of the flap valves.
The disadvantage of this known technical solution is that the flap valves can assume only two operating states. It would be desirable, however, if the flap valves were continuously adjustable with defined valve positions. For a continuous operation of the valves, the compensation of the tolerances by means of the elastic connecting rod would have to be eliminated. This would be possible only if the intake manifold or the control components were produced with very close manufacturing tolerances, which is not economically feasible.
The object of the invention is to provide an intake manifold with continuously adjustable flap valves, the production of which is economically competitive with the known solutions for flap valves. This object is attained by the features of by the invention as described and claimed hereinafter.
The intake manifold according to the invention has flap valves that are arranged in the intake channels of the intake manifold between the plenum and the cylinder-side outlet. The flap valves are controlled, for example, by valve cranks or gears. An actuator transmits the switching power, for instance through a rod assembly via the control, to the flap valves. The actuator must ensure the continuous adjustability of the valves. The mechanical couplings between valve gear, flap valves and actuator must be free of play. Only this makes it possible to obtain a precisely defined valve position as a function of the actuator position. To ensure that the flap valves have always the same position in relation to one another, the manufacturing tolerances in the intake manifold and the flap valve system must be compensated. For this purpose an adjustment is provided, which is preferably integrated in one of the mechanical couplings. The adjustment must be made in such a way that the position of each individual flap valve can be changed and subsequently fixed.
If the flap valves are arranged in the vicinity of the cylinder intakes, the precisely defined position of the valves can be used to produce a swirl in the flow within the combustion chamber of the cylinder. This has the advantage that a better mixture is formed in the partial load range of the engine, which can reduce fuel consumption and harmful emissions. The progressive adjustability further makes it possible to arrange flap valves in all intake channels leading to the cylinders. Of course then not all of the valves may be fully closed, since the air supply would in this case be completely shut off.
An advantageous embodiment of the inventive concept provides that the adjustment be made directly on the actuator. This may be accomplished, for instance, by means of a clamping plate into which the individual control rods to the valve cranks are clamped. This has the advantage that the adjustment can be mounted in the center of the cylinder-side intake manifold flange so that it is readily accessible. This makes it easier to readjust the flap valves during maintenance work.
A particular embodiment of the invention provides that the control rods be made of a strand-like semi-finished part on which a bushing is mounted as a joint, which is inserted onto bearing pins of the control. The control rods may for instance be made of a wire, the ends of which are coiled into helical springs. The bushing is pressed into the helical winding. Also feasible is a U-profile that is fixed directly to the bushing, for instance by a soldered connection. The use of semi-finished parts for the valve gear increases the economic efficiency of the proposed solution.
If the adjustment is provided on the flap valve actuator, it is advantageous to make the distance between the rotary axis of the actuator and the clamping elements and between the flap valve axes and the valve controls equal in length. As a result the control rod executes a purely translatory movement when the flap valves are operated. The clamping elements on the actuator can therefore be rigid since no rotational relative movements occur between the control rods and the actuator.
In another variant of the invention, the adjustment is integrated in the mechanical coupling between the drive of the flap valves and the power transmission. This arrangement has the advantage that power transmission can be effected through a single component, e.g. a connecting rod. An advantageous variant in this type of construction is a toothed belt for power transmission. Gears are used as drives, and the adjustment may be realized in that the gear teeth are rotated and fixed on a base body. It is likewise possible to effect the positional fixation between the valve axis and the gear. Since the toothed belt is a standard component, it is an extremely cost-effective option to ensure power transmission between the actuator and the flap valves.
According to one particular embodiment of the invention, the control of the flap valves is ensured by dual levers that are coupled with two cable pulls at their ends. The flap valves can be adjusted by means of clamping connectors at the ends of the dual levers. Power transmission by cable pulls has the advantage that the actuator may be placed at any point within the engine compartment by redirecting the cables. This is particularly advantageous if no installation space for the actuator can be provided near the intake manifold.
In a further variant of the invention the adjustment is provided in the mechanical coupling between the flap valve axis and the valve cranks or gears acting as the control. The valve crank may for instance be inserted into a bore of the valve axle. The two components may be connected, in particular, by means of an adhesive bond. Alternatively, gear teeth may be provided in the plug-in connection between valve crank and valve axle. If a bonded connection is used, it is advantageously designed to be elastic. Since in the valve positions between the limit stops the forces acting between the valves are small, a defined position in the control range of the valves is ensured despite the elasticity of the bonded connection. In the stop positions of the valves, however, the elasticity of the bonded connection can additionally compensate tolerances to a limited extent. This solution thus combines the advantageous functional principles of the known solutions with those of the solution according to the invention.
In one particular embodiment the flap valves being used are assembly-injection molded valve modules that can be mounted on the intake manifold. This measure increases the economic efficiency of the solution.
To produce the intake manifold according to the invention a method is provided which permits efficient calibration of the flap valves during assembly. This is achieved by using a gauge or jig that brings the flap valves into the desired position relative to one another and to the actuator. After preassembly of the valve gear and the actuator, the adjustments can now be fixed. As a result, the positions of the flap valves relative to one another are unchangeable. Any manufacturing tolerances are automatically compensated. At the end of the assembly process, the gauge is removed again.
These and other features of preferred embodiments of the invention are set forth in the claims as well as in the description and the drawings. The individual features may be implemented either alone or together in the form of subcombinations in embodiments of the invention or in other fields of application and may represent advantageous embodiments that are protectable per se, for which protection is hereby claimed.